Pressure control system with safety feature assuring two-hand operation



May 30, 1961 R. NowAcK PRESSURE CONTROL SYSTEM WITH SAFETY FEATURE AssURING Two-HAND OPERATION Filed June 24, 1960 DELIVERY PRESSURE CONTROL SYSTEM WITH SAFETY FEATURE ASSURING TWO-HAND OPERATION Rudolf Nowack, Hannover, Germany, assigner to Westinghoie Bremsen Gesellschaft, m.b.'H., Hannover, Germany Filed June 24, 1960, Ser. No. 38,567

i Claims priority, application Germany July 2, 1959 8 Claims. (Cl. 121-38) This invention relates to uid pressure operable control apparatus for controlling supply of iluid under pressure to auid pressure operable device, and, more particularly, to such controly apparatus embodying a safety feature necessitating and assuring use of both hands by the operato'r in operating the control apparatus.

Certain fluid operation operable machine tools are, by the nature of the operation performed thereby, inherently dangerous to the operator While operating such machine. For example, a lluid pressure operated punch machine may be provided with a clamp for retaining the item to be punched in position in order that the operator may keep his hands at a safe distance from the punching tool during the operating cycle. In order to speed up productivity, however, the operator may ignore the clamp and merely hold the item in position with one hand while using the other hand to operate a lever on a valve that sets the machine in motion. Consequently, efforts to overcome this problem have been made by providing two control valves arranged in series and in such manner as to require the use of both hands of the operator to operate respective levers of the valves to put the machine into operation. In many instances the operator has bypassed this safety feature by simply tying down the operating lever of, and thereby blocking out, one of the valves, thus requiring the operator to use one hand only for oper ating the other valve.

The object of the present invention, therefore, is to provide a iluid pressure control apparatus necessitating the use of both hands of the operator simultaneously during operation. Essentially, the invention comprises two liuid pressure operable control valve devices serially interposed in a uid pressure supply conduit leading from a source of uid under pressure to a fluid pressure operable device or machine desired to be operated, the latter being supplied with iluid under pressure only when the two control valve devices simultaneously occupy a supply position'to open the communication through the conduit from the source to the device to be operated. Operation of the two control valve devices is effected respectively by a pair of pilot valve devices for causing operating fluid pressure to be supplied to said control valve devices, it being necessary to operate both pilot valve devices simultaneously to eifect simultaneous operation of the control valve devices. Otherwise, if just one of the pilot valves is operated, `iluid pressure is supplied to the respective control valve device controlled by said one pilot valve device for operating it to its supply position while the same degree of iluid pressure is also supplied, through a restricted communication from Said one pilot valve to the other control valve device, to act on a lockout piston along with a biasing spring for retaining said other control valve in a cut-olf position to prevent ow of liuid under pressure therethrough even though the other pilot valve is then later and independently operated to a position for supplying said other control valve with operating pressure. Since each control valve is provided with a lockout piston, it is immaterial which pilot valve is operated, for, if it is operated independently of the other pilot valve, the other control valve will remain in its cut-off position until the one pilot valve is released and both pilot valves are operated .Y

simultaneously.

In a modified version of the invention the control valve i. devices are operated by manually operable plungers, thereby eliminating the necessity for pilot valves for the control valve devices. Each control valve device has has a lockout piston device that acts to lock the respective plunger in a non-operative position when one of the plungers is operated independently of the other.

in the drawings, Fig. l represents a schematic viewof a fluid pressure control apparatus embodying the inven.- tion, and Fig. 2 is a modified version of the arrangement shown in Fig. 1.

Description and operation-Fig. 1

Referring to Fig. 1 of the drawing, the uid pressure operable control apparatus embodying one form of the invention comprises two fluid pressure operable controlV valve devices 1 and 2 serially interposed in a liuidpres-` sure. conduit consisting of a supply side or portion, 3 leading from a source of uid under pressure (not shown);

to an inlet port 4 of the control valve device 1, an interconnecting portion 5 connecting a delivery port 6 of the control valve device 1 with an inlet port 7 of the control valve device 2, and a delivery side or portion 8 leading through conduits 13 and 14 to the control valve devices. 1 and 2, respectively, for a purpose hereinafter disclosed.-

Since it is not deemed essential to the understanding of the invention, the details of the pilot valve devices 11 and 12! have been intentionally omitted in the drawing. Briey, each of the pilot valves 11 and 12 may comprise a valve (not shown) biased toward a closed position, in which fluid pressure communications 15 and 16, indicated diagrammatically in the drawing by broken lines, in the valve devices 11 and 12 respectively, are closed, ,Manually operable handles 17 and 18 are provided on the pilotvalve devices 11 and 12, which handles are biased toward respective normal positions, in which the valves in said pilot valve devices occupy their closed positions, and are` manually operable to respective operating positionsin which the. valves in said pilot valve devices are operated to respective open positions whereby the communica-tions 15 and 16 are opened to connect branch supply conduitv 10 to conduits 13 and 14, respectively.

Since the control valve devices 1 and 2, as shown, are l. identical in structure, similar components thereof, withv certain exceptions, will be designated by similar reference numerals. Each of the control valve devices 1 and 2. comprises a casing 19 having at one end thereof a pressure chamber 20, to which conduits 13 and 14, respective ly, open, and at the other end a control chamber 21, The Y control valve devices 1 and 2 are shown partly in diagrammatic form in the drawing with only certain components being shown in detail, such showing thereof being considered adequate for a clear understanding of the invention. A piston assemblage 22 is axially operable within w the casing 19 and comprises an operating piston 23 having v one side thereof adjacent the pressure chamber 20 sub.- jected to the prevailing iluid pressure therein, and a lockout piston 24 having one side thereof adjacent the control chamber 21 subjected to the prevailing uid pressureiri said control chamber. The effective pressure areas 'of both pistons 23 and 24 are equal for a purpose to'be' hereinafter explained. Thevoperating piston 22 and .the

Patented May 30, 1961 lockout piston 23 are axially spaced on opposite ends of a connecting stem 25 in coaxial relationship.

Though not shown in the drawing, the connecting stem 25 of control valve device 1 carries valve means, such as a 'spool valve, for example, movable with' the piston assemblage 22, said piston assemblage and'valve'means having respective normal positions in which a communication 26 between delivery port 6- and a rst atmospheric vent port 27 and a communication 28 between a port 29, connected by a conduit 30 to conduit 14, and a port 31, connected by a conduit 32 to control chamber 21, are established by said valve means,`said communications being indicated diagrammatically in the drawings as solid lines. The piston assemblage 22 and, therefore, the valve means carried on stem 25 are operable, responsively to fluid pressure in chamber 20 acting on piston 23, to respective supply positions in which communicattions 'Z6-and 28 are disestablished, and a communication 33 between inlet port 4 and delivery port 6 anda communication 34 between port 31 and a second atmospheric port 35 are established by said valve means. A spring 36 is interposed between operating piston 23 and a radially formed Wall 37 in casing 19, said wall having a concentric bore through which stem 25 may freely move. Spring 36 is effective for returning piston assemblage 22 and the valve means carried thereon to their normal positions upon relief of fluid pressure from pressure chamber 20 through conduit 13 and an exhaust communication 38 in the pilot valve device 11 when the valve in the pilot valve device is'in its closed position.

The control valve device 2 being identical in structure to the control valve device 1, also comprises valve means carried on a connecting stem 25, a communication 26 (connecting atmospheric port 27 with delivery port 9), communications 28, 33 and 34, ports 27, 29, 31 and 35, conduit 32, spring 36 anda wall 37. A conduit 39 connects port 29 of control valve device 2 to conduit 13. Pilot valve device 12 is provided with an exhaust communicattion 40, serving a purpose similar to communication 38 in pilot valve device 11. Chokes 41 and 42 are interposed in conduits 30 and 39, respectively, for restricting flow of fluid under pressure therethrough for a purpose to be hereinafter disclosed.

In considering the operation of the control apparatus as disclosed in Fig. l and above described, let it be assumed that conduit 3, and therefore conduit 10, are charged with uid under pressure from the source (not shown) to which said conduit 3 is connected. `If the oper- :ttor desires to effect supply of fluid under pressure to conduit 8, which leads to the machine or device, neither of which is shown, desired to be operated, he depresses both handles 17 and 18`of the respective pilot valve devices 11 and 12 simultaneously, or as nearly simultaneously as possible, whereupon communications 15 and 16 are opened and iuid` under pressure ows to conduits 13 and 14 and to pressure chambers 20 of the control valve devices 1 and 2, respectively.

Fluid pressure in chambers 20 acting on pistons 23 cause the piston assemblages 22 and the valve means carried thereon to be operated to'their respective supply positions in which, as above noted, communications 26 and 28 are disestablished and communications 33 and 34 are established in the control valve devices 1 and 2, respectively, whereby fluid under pressure may ow from conduit 3, through communication 33 in control valve device 1, through connecting conduit 5. and through communication 33 in control valve device 2 to conduit 8 leading to the device to be operated. Such supply of fluid under pressure continues as long as the operator maintains both handles 17 and 18 depressed.

Though not mentioned above, it will be noted that when the operator simultaneously depresses handles 17 and 18 of the pilot valve devices 11 and 12, in addition to uid under pressure flowing to conduits 13 and 14, uid under pressure also ows to branch conduits 30 and 39,

but because of the restriction of ow through Chokes 41 and 42, iluid pressure builds up faster in chambers 20 than in chambers 21, which are connected to said conduits 30 and 39, in the normal positions of the piston assemblages 22, by way of respective communications 28 in valve devices 1 and 2 and by way of the respective conduits 32. Faster duid pressure build-up in` chambers 20 than in chambers 21 is effective for overcoming the combined opposing respective forces of springs 36 and any sub-maximum pressure `build-up in chambers 21 for operating the piston assemblages 22 to their respective supply positions in which fluid under pressure may ow to conduit 8, as above described.

If, however, one or the other of handles 17 and 18 of the pilot valve devices 1 and 2, it being immaterial which one, is released while the pistonassemblages 22 are in their respective supply positions, or if upon initial operation of said handles one of them, it again being immaterial which one, is depressed suiciently ahead in time of the other, depending upon therestricting rate of `chiolres 41 and 42, flow of fluid under pressure to delivery conduit 8 is either terminated or is prevented from being initiated, respectively. This is due to the safety feature of the invention to be presently described. Of course, it should be apparent that the operator can also terminate supply of fluid under pressure from conduit 3 to conduit 8 by releasing both handles 17 and 18 in which event fluid pressure in both chambers 20 is vented by way of conduits 13 and 14 and communications 38 and 40 in the pilot valve devices 1 and 2, respectively, permitting springs 36 to return the respective piston assemblages 22 to their normal positions.

In considering the safety feature of applicants invention, let it be assumed that only handle 17 of pilotvalve device 1, for example, is depressed to thereby open oommunication 15 whereby fluid under pressure may flow from conduit 10 to conduit 13 and conduit 39 only, cornmunication 16 in pilot valve device 2 remaining closed. Fluid pressure supplied from conduit 13 to chamber 20 of control valve device 1 acts on piston 23 to move piston assemblage 22 to its supply position in which communications 26 and 28 in control valve device 1 are disestablishedand communications 33 and 34 are established. At the same time, fluid under pressure may flow, at a restricted rate, from conduit 13, through conduit 39, choke 42, communication 28 in control valve device 2, and conduit 324 leading to control chamber 21 of control valve device 2 to charge said control chamber with fluid pressure acting on lockout piston 24. Upon termination of a certain uniform time interval after the charging of control cliamber 21 of control valve device 2 is initiated, said control chamber is charged with uid at the pressure prevailing at the source, said time interval being determined by a preselected ow capacity of choke 42. It is to no avail, thereafter, for the operator to depress handle 18 of pilot valve device 2, for uid pressure thus supplied to chamber 20 of control valve device 2 and acting on piston 23, being the same as uid pressure in chamber 21, is ineffective for overcoming the combined opposing forces of spring 36 and uid pressure acting on piston 24 which, as above noted, is of equal effective pressure area as piston 23. Piston assemblage 22 of control valve device 2, and therefore, the valve means associated thcrewith, are effectively locked in their respective normal positions to block any ow of fluid pressure supply through control valve device 2 to conduit 8 until both handle 17 and 18 are released, at which time control chamber 2l of control valve device 2 is vented by way of conduit 32, communication 28, conduit 39 and exhaust communication 38 of pilot valve device 1, after which venting both said handles may be depressed simultaneously to effect supply of fluid pressure from conduit 3 to conduit, as above described.

If, after having depressed both handles 17 and 18 simultaneously for eifecting ow of `uid pressure from conduit 3 to conduit 8, the operator releases only one of.E said handles, say handle"18,`for eXample,-while`mintaining' the other depressed, chamber 20 of control lvalve dvice 2 is vented to atmosphere by way of conduit 14 and communication 40 in pilot valve device 2 to permit piston assemblage 22 of control valve device 2 to be returned to its normal position by spring 36. With piston assemblage 22 in its normal position, communication 33 is disestablished and communication 28 in control valve device 2 is established to permit chamber 21 to be charged with fluid pressure from conduit 39 to `act on lockout piston 24 which, with spring 36, eifectively maintains or locks piston assemblage 22 in its normal position, as above described, to block iiow of uid under pressure through control valve device 2 to conduit 8 until handle 17 also is released and both handles are depressed simultaneously.

It should be evident that it is immaterial which of the handles 17 or 18 is operated independently of the other, for'in either case control chamber 21 of one or the other of the control valve devices 1 or 2 will'be charged with fluid pressure, as above described, to lock the piston assemblage 22 of the respective control valve device in its normal position.

Description and operation-Fig. 2

A modified version of the invention is represented by Fig. 2 of the drawing wherein two control valve devices 43 and 44 are shown. Since the Itwo control devices 43 and 44 are identical in structure, similar reference numerals, with certain exception, will be applied to similar components. A uid pressure supply conduit 45 is connected to an inlet port 46 on control valve device 43 and a branch conduit 47 from said supply conduit is connected to similar respective ports 48 on the two control valve devices 43 and 44. A connecting conduit 49 connects a delivery port 50 on the control valve device 43 to an inlet port 51 on the contr-ol valve device 44, while a delivery conduit 52, leading to a uid pressure operable device (not shown) to be controlled by the control apparatus, is connected to a delivery port 53 of control valve device 44. Each of the control valve devices 43 and 44 is provided with two atmospheric vent ports 54 and 55.

Each of the control valve devices further comprises a casing 56 having therein an axially operable valve assemblage 57, the details thereof not being considered essential to a clear understanding of the operation of the invention and therefore not shown. The valve assemblage 57 comprises an axially movable stem 58 on which a valve member (not shown) is carried for movement therewith. One end of the stem 58 is engaged by one end of an axially aligned manually operable plunger 59, which has its other end projecting exteriorly of they casing 56 for manipulation by the operator, while the other end of said stem carries a bearing plate 60 against which a spring 61 is compressed for urging the valve assemblage 57 and the plunger 59 toward a respective normal position in which a communication 62, between port 54 and delivery port 50 in control valve device 43 and between port 54 and delivery port 53 in control valve device 44, and a communication 63, between ports S5 and similar ports 64 in both said control valve devices, are established, said communications being diagrammatically indicated by respective solid lines in the drawing. Also while in its normal position the valve assemblage 57 in each of the control valve devices 43 and 44 serves to disestablish a communication 65 between port 48 and port 64 and a communication 66 between inlet port 46 and delivery port 50 in control valve device 43 and between inlet port 51 and delivery port 53 in control valve device 44, both said communications being diagrammatically shown by respective broken lines in the drawing.

The primary difference between the control apparatus shown in Fig. 1 and that shown in Fig. 2 is that the valve assemblages 57 in the control valve devices 43 and 44 in Fig. 2 are operated by manual forces applied directly thereto through the plungers 59, respectively, rather than by'fo'rcesf-exerted by fluid-pressure as are the piston`.as-

sembl'ag'es 22V in' control valve devices l'and 2 in Fig."1.'f

Moreover, instead of having a locking piston acting to lock the valve assemblage 57 in its normal position, such* as locking piston 24 does in locking piston assemblage 22 in its normal position in control valve devices 1 and 2, the control valve devices 43 and 44 are each provided with a fluid pressure operable lockout device 67, which acts, in a manner hereinafter described, to lock the plunger 59 in its normal position or a non-operative state in which it is rendered ineffective for moving the valve assemblage 57 out of its normal position. When the plungers 59 are free to move, they may be manually operated downwardly, as viewed in the drawing, for moving valve assemblage 57 against the opposing force of spring 61 to a supply position in which communications 62 and 63 are disestablished'and communications 65 and 66 areestablishe'd.

Each of the lockout devices 67 comprises a piston 68 disposed axially perpendicular to the axis of plunger 59 and subjected on one side to uid pressure prevailing in a pressure chamber 69 in the casing 56 while having coaxially extending-from its other side and movable there` with a stem 70, the free end of which, in its normal posi-- tion and that of said piston, remains clear of the plunger 59 upon downward movement of the latter. Responsive-- ly to iluid pressure in chamber 69, however, acting on the one side of piston 68, said piston and stem 70 move out of their normal position, against the opposing force of a' spring 71 acting on the opposite side of said piston, to al locking position defined by abutting engagement of the free end of stern 70 with plunger 59 (as shown in broken l outline in the drawing), in which locking position plunger 59 is restrained from movement out of its normal position by a shoulder 72 formed on said plunger which engages said stem and thereby prevents said plunger from being moved downwardly to an operating position for moving valve assemblage 57 to its supply position.-

Chamber 69 of the lockout device 67 on control valve device 43 is connected by a conduit 73, with a choke 74 interposed therein, to port 64 on control valve device 44,

while chamber 69 of lockout device 67 on the control valve device 44 is connected by a conduit 75, with a choke 76 inter-posed therein, to port 64 on control valve device 43.

In operation, if the operator desires to elfect supply of iluid under pressure from the supply conduit 45 to the delievery conduit 52 leading to the device to be operated (not shown), he must simultaneously or as nearly simultaneously-as possible depress both plungers 59 of the control valve devices 43 and 44 to their respective operating positions for moving the valve assemblages 57 to their through conduits and 73 to chambers 69 of the lockout devices 67 on the control valve devices 43 and 44,

respectively. The chokes 74 and 76, however, being of a preselected ilow capacity, restrict flow of iluid under pressure suiciently to momentarily delay effective build-up of uid pressure in the respective chambers 69 for a certain time interval and thereby delay movement of pistons 68 and stems 70 to their locking positions a corresponding interval of time to permit shoulders 72 of the respective v plungers 59 to move past the ends of stems 70 to prevent locking engagement of said plungers when they are operated simultaneously. r

lf, however, (l) after the plungers 59 have beenmoved to their'respective operating positions,.one of saidV plungers is released to permit the respective spring 61 to return it and the respective valve assemblage 57 to their respective normal positions, or (2) if only one of said plungers is initially operated to its operating position, say plunger 59 of the control valve device 43, for example, in case (l) stem 70, which is already resting against plunger 59 above shoulder 72 due to uid pressure acting on piston 68, will move underneath shoulder 72 to its locking position upon complete return of said plunger to its normal position, and in case (2) build-up of fluid pressure in chamber 68 of the locking device 67 of control valve device 44 will cause stem 70 of said locking device to be moved over into locking position underneath shoulder 72 and thereby, in each case, render inelective any further efforts to operate plunger S9 of control valve device 44 to its operating position until plunger 59 of control valve device 43 is released to permit uid pressure in chamber 69 of control valve device 44 to be released by way of conduit 7S and communication 63 through vent port 55. Upon release of uid pressure from chamber 69, spring 71 returns piston 68 and stem 70 to their respective normal positions so that said stem is out of engagement with shoulder 72, thereby placing the control apparatus in condition for effective operation to supply uid under pressure from conduit 45 to conduit 52, as above described.

It should be apparent, as is the case in the control apparatus shown in Fig. l, that, with respect to the control apparatus shown in Fig. 2, it is immaterial which one of the plungers 59 is operated independently of the other, for in either case the lockout device 67 of one or the other of the control valve devices 43 and 44 will operate to lock the other plunger in a non-operative state.

Having now described the invention, what I claim as new and desire to secure by Letters Patent, is:

l. A control apparatus for controlling supply of uid under pressure to a uid pressure operable device, said control apparatus comprising, in combination, a conduct through which iiuid under pressure may ow to the uid pressure operable device, a pair of control valve devices interposed in said conduit in serial relation to each other and comprising a pair of respective valve members effective in respective normal positions, either alternatively or at the same time, for interrupting flow of uid under pressure through said conduit, said valve members being alternatively or simultaneously operable to respective supply positions and being effective, when simultaneously operated to said respective supply positions, for establishing communication through said conduit for flow of tluid under pressure, and means associated with said valve members and eiective in response to a control impulse imparted by operation of one of said valve members to its supply position and following the expiration of a certain uniform interval of time after said one valve member is operated to its supply position for preventing operation of the other of said valve members out of its normal position provided said other valve member is in its normal position at the expiration of said interval of time.

2. A control apparatus for controlling supply of fluid under pressure to a fluid pressure operable device, said control apparatus comprising, in combination, a conduit through which fluid under pressure may flow to the uid pressure operable device, a pair of control valve devices interposed in said conduit in serial relation to each other and comprising a pair of respective valve members eifective in respective normal positions, either alternatively or at the same time, for interrupting flow of uid under pressure through said conduit, said valve members being alternatively or simultaneously operable to respective supply positions and being effective, when simultaneously operated to said respective supply positions, for establishing communication through said conduit for flow of fluid under pressure, and means including a pair of lockout-members associated respectively with the said valve members and effective in response 'to a control impulse imparted by operation of one of said valve members to its supply position and following the expiration of a certain uniform interval of time after said one valve member is operated to its supply position for causing the corresponding one of said lockout members to prevent operation of the other of said valve members out of its normal position provided said other valve member is in its normal position rat the expiration of said interval of time.

3. A control apparatus for controlling supply of [luid under pressure to a uid pressure operable device. said control apparatus comprising, in combination, a conduit through which tiuid under pressure may flow to the tiuid pressure operable device, a pair of control valve devices interposed in said conduit in serial relation to each other and comprising a pair of respective valve members elective in respective normal positions, either alternatively or at the same time, for interrupting iiow of uid under pressure through said conduit, said valve members being alternatively or simultaneously operable to respective supply positions and being effective, when simultaneously operated to said respective supply positions, for establishing communication through said conduit for flow of uid under pressure, a pair of lockout members associated respectively with said Valve members, either one of said lockout members being operatively responsive, provided the associated valve member is in its normal position and the other valve member has been operated to its supply member, to a control impulse imparted to the said one of said lockout members by operation of the other valve member to its supply position for preventing operation of said one valve member to its supply position, and means for delaying operative response of said one lockout member to the control impulse for a certain uniform interval of time following operation of said other valve member to its supply position.

4. The combination as defined in claim 3, further characterized by a pair of respective manually operable members for effecting operation of said pair of valve members to their respective supply positions, either alternatively or simultaneously, said manually operable members being so spaced on the control apparatus as to require the use of both hands of the operator when operating them simultaneously.

5. A control apparatus for controlling supply of uid under pressure to a iiuid pressure operable device, said control apparatus comprising, in combination, a conduit having a supply portion and a delivery portion and through which supply of uid under pressure may iiow to the iiuid pressure operable device, a pair of control valve devices serially interposed in said conduit for controlling said flow of fluid under pressure therethrough, said control valve devices each including `a valve member biased toward a normal position, in which said ow of uid under pressure is interrupted, and each of said valve members being alternatively operable respoilsively to an operating force exerted thereon to a supply position in which communication through said conduit is established for ow of uid under pressure, provided both valve members are in their respective supply positions at the same time, a pair of manually operable devices so spaced on the control apparatus as to require the use of both hands of the operator for simultaneous operation of said manually operable devices out of respective normal positions in which said valve members are in their respective normal positions, to respective operating positions in which respective operating forces are caused to be exerted on said valve members for operating them to their respective supply positions, and means including a pair of lockout members associated respectively with the said valve members and effective in response to uid pressure supplied thereto by operation of one of said valve members to its supply position and following expiration of a certain uniform interval of time after said one valve member is operated -to its supply position, in which a uid pressure communication from said supply portion of said conduit to the 9 corresponding lockout member associated withthe other valve member is established, for causing said corresponding llockout member to prevent operation of said other valve member out of its normal position provided said other valve member is in its normal position at the expiration` of said interval or' time.

6. A control apparatus for controlling supply of fiuid under pressure to a iiuid pressure operable device, said control apparatus comprising, in combination, a conduit having a supply portion and a delivery portion and through which supply of fiuid under pressure may fiow to the fluid pressure operable device, a rst control valve device interposed in said conduit, a second control valve device interposed in said conduit in series with said first control valve device and cooperativetherewith for controlling flow of fluid under pressure through said conduit, independently operable valve members in each of said control valve devices having respective normal positions in which said fiow of fiuid under pressure through said conduit is interrupted and being operable in response to respective operating forces exerted thereon to respective supply positions in which communication through said conduit for ow of uid under pressure is established, provided said valve members are operated to their supply positions simultaneously, respective biasing means for restoring said valve members to their said normal positions upon removal of said operating forces acting thereon, respective manually operable means operable out of respective normal positions, in which said valve members are free of any operating forces, to respecive operating positions to cause respective operating forces to be exerted on said valve members, said manually operable means being so spaced on the control apparatus as to require the use of both hands of the operator when operating them simultaneously, and a pair of fluid pressure operable lockout members associated respectively with said control valve devices, one or the other of said lockout members, but only one at any given time, being effective in response to fluid pressure supplied thereto from said supply portion of said conduit through a communication established by operation of the other of said valve members to its supply position and following expiration of a certain uniform interval of time after said other valve member is operated to its supply position for causing said one lockout member to prevent operation of the corresponding valve member out of its normal position, provided said corresponding valve member is in its normal position at the expiration of said interval of time, whereby ow of fiuid under pressure through said conduit is inhibited.

7. A control apparatus for controlling supply of uid under pressure to a fluid pressure operable device, said control apparatus comprising, in combination, a supply conduit through which iiuid under pressure may flow from a supply portion of said conduit to a delivery portion thereof to the fluid pressure operable device, a first control valve device interposed in said conduit, a second control valve device interposed in said conduit in series with said first control valve device, first fiuid pressure operable valve means in said first control valve device, second iiuid pressure operable valve means in said second control valve device, a first pilot valve device for controlling iiuid pressure supply from said supply portion of said conduit to said first valve means, a second pilot valve device for controlling supply of fiuid pressure from said supply portion of said conduit to said second valve means, each of said pilot valve devices having a normal position in which fluid pressure is cut off from the respective valve means and being manually and alternatively operable to an operating position in which fluid pressure is supplied to the respective valve means, said first valve means and said second valve means each having a normal position in which ow of fluid under pressure through said conduit between said supply portion and said delivery portion is interrupted and each being operable responsively to fluid pressure to a supply position in which communication through said conduit for -ow of uid under pressure between said supply portion and said delivery portion is established, provided both said valve means are in their respective supply positions at the same time, respective biasing means for restoring said first valve means and said second valve means to their respective normal positions upon relief of fluid pressure acting thereon, a first lockout piston operatively associated with said first valve means, a second lockout piston operatively associated with said second valve means, one of said lockout pistons acting cooperatively with the respective said biasing means, when subjected to fluid pressure on one side and upon termination of a certain-uniform time interval following operation of the other valve means to itssupply position, for maintaining the respective said valve means in its said normal position, said one side of said one lockout piston being subjected to fluid pressure from said supply portion of said conduit through a uid pressure communication established by the respective said valve means in its said normal position and by the other pilot valve device in its said operating position, said one side of said one lockout piston being relieved of fluid pressure acting thereon upon restoration of said other pilot valve device to its said normal position, and choke means provided in said communication for delaying effective build-up of fluid pressure acting on said one side of said one lockout piston until expiration of said certain uniform time interval.

8. A control apparatus for controlling supply of fiuid under pressure to a fluid pressure operable device, said control apparatus comprising, in combination, a supply conduit through which fiuid under pressure may liow from a supply portion of said conduit to a delivery portion thereof to the fluid pressure operable device, a first control valve device interposed in said conduit, a second control valve device interposed in said conduit in series with said first control valve device, a first valve member in said first control valve device, a second valve member in said second control valve device and cooperating with said rst valve member for controlling iiow of fiuid under pressure through said supply conduit, each of said valve members having a respective normal position in which flow of fluid under pressure through said conduit is interrupted and each being operable to a respective supply position in which communication through said conduit is established for permitting flow of iiuid under pressure therethrough, provided both said valve members are in their respective supply positions at the same time, a first manually operable plunger for exerting a force on said first valve member for operating it to its said supply position, a first biasing spring for restoring said first valve member to its said normal position upon release of said force acting thereon, a second manually operable plunger for exerting a force on said second valve member for operating it to its said supply position, a second biasing spring for restoring said first valve member to its said normal position upon release of said force acting thereon, said first and said second plungers being independently and alternatively operable but being so spaced on said control apparatus as to require the use of both hands of the operator for simultaneous operation thereof, a first lockout device associated with said first control valve device, said first lockout device having a normal position out of engagement with said first plunger and being operable responsively to fluid pressure, upon termination of a certain uniform time interval following operation of said second valve member to its supply position independently of said first valve member, in which supply position of said second valve member a first fluid pressure communication from said supply portion of said conduit to said first lockout device is established, to a locking position into engagement with said first plunger for locking said first plunger in a non-operative state, a second lockout device associated with said second control valve device, said second lockout device having a normal posi- 1 l tion out of engagement with said, second plunger and beingoperable responsivelyfto fluid pressure, upon termination of a certain uniform time interval following operation of said first valve member to its supply position independently of said second valve member, in which supply position of said rst valve member a second fluid pressure communication from said supply portion of said conduit to said second lockout device is established, to a locking position into engagement with said second plunger for locking said second plunger in a non-operative state, and respective choke means provided in both said fluid pressure communications to said rst and said second lockout devices for delaying effective fluid pressure action on 12 the respective said lockout devices until expiration of said uniform time interval when both said rst and said second plunger are operated simultaneously, to thereby provide suiiicient time for simultaneous operation of said valve members to their respective supply positions.

References Cited in the le of this patent UNITED STATES PATENTS 2,313,869 Gayring Mar. 16, 1943 2,383,851 Gayring Aug. 28, 1945 2,451,010 Yanchenko Oct. 12, 1948 

